   (if (empty? downstream)
     []
     [[:message-envelope
-      (rand-nth (seq downstream))
+      (rand-nth* (seq downstream))
       :forwarded-subscription
       subscription
       (get-envelope-id)]]))

(s/defn do-probability :- s/Bool
  "'rand is inclusive of 0 and exclusive of 1, so our test should not have '=."
  [cutoff :- ProbabilitySchema]
  (< (rand) cutoff))

(s/defn forward-subscription :- [MessageEnvelopeSchema]
  "Take a node's 'downstream map and a new 'subscription.


    ;; Forward subscription to :downstream.
    (let [downstream (seq downstream)
          downstream+ (reduce (fn [x _] (conj x (rand-nth* downstream)))
                              downstream
                              (range (:connection-redundancy config)))]
      (map
